1. Field of the Invention
The present invention relates to a transparent immobilization device which is provided to cover at least a part of a patient's body that needs to be fixed, supported and/or immobilized, wherein the immobilization device is at least partly made of a plastic material.
2. The Prior Art
Immobilization devices are frequently used in radiation therapy and diagnostic imaging for the purpose of immobilizing a body part in a fixed and reproducible position with respect to an irradiation source, in orthopedic applications for the purpose of immobilizing inflamed or injured joints in case of trauma or diseases, for supporting and immobilizing ligaments and muscular structures, in physical rehabilitation applications and in podiatry for example as insole (foot-bed) applications. A wide variety of plastic materials have been used in the art for making in orthopedic or other fixation or immobilization devices. However, only a limited number of plastic materials have a melting temperature which is sufficiently low to permit direct molding to the patients' body without causing burn injuries. Amongst those plastic materials, only a limited number have a sufficient formability and elasticity in the molten state at a temperature which can be supported by the body, to permit direct molding on a patients' body. Direct molding to the patients' body is important, as it permits adapting the size and shape of the immobilization device directly to each individual patient, in the position in which the body part is to be immobilized. Examples of plastic materials suitable for direct molding to a body part include thermoplastic materials for example polyurethane, trans-polyisoprene, polyesters for example polycaprolactone or blends of two or more of these materials.
However, the hitherto used materials are opaque, they are non-transparent. As a consequence, they do not permit observing the skin covered by it, nor do they permit adjusting the positioning of the material using markers present on one or both of the immobilization device and the body part to be covered by the plastic material. This is a serious disadvantage in applications such as radiation therapy and diagnostic imaging, where it is of utmost importance that with intermittent treatments, a highly reproducible re-positioning and fixation of the immobilization device is provided and that a reproducible positioning, fixation and immobilization of the body part in a desired position may be guaranteed. Besides being opaque, the known plastic materials are quite rigid and hard which goes at the expense of the wearing comfort and they show significant shrinking upon crystallization when cooling down from the melting temperature. As the immobilization device in the course of the molding is usually is formed in such a way that it fits as close as possible to the body part to be immobilized, there is a risk that it fits too tightly after cooling and crystallization and feels uncomfortable to the patient.
A vast number of the industrially available engineering plastic materials have a melting temperature which is above 100° C. These materials may be suitable for use in immobilization structures as well, provided they are molded using a positive mold which is made to correspond as close as possible to the body part to be immobilized. This thus involves the additional step of producing a positive mold which must correspond as closely as possible to the body part to be immobilized.
It is therefore the object of the present invention to provide a transparent immobilization device which may be directly molded onto the body part that needs to be immobilized to fit to it as closely as possible, but which still leaves the possibility of moving the body part within pre-determined limits.